Hatwaed a



(No Model.)

H. A. HARVEY.

METHOD OF MAKING ROLLED WOOD SCREWS.

No. 329,900. Patented Nov. 10, 1885.

PETERS. PhMo-mM npMr, Wnhingm D. C.

HAYWARD A. HARVEY, OF ORANGE, NEW JERSEY.

METHQQ OF MAKING RQLLED WOOD-SCREWS.

.LJhcadrZCri'E-EQIQ' forming part of Letters Patent No. 329,900, dated November 10, 1885.

Application filed January 1885. Serial No. 152,553. (No model.)

To all whom, it may concern:

Be it known that I, HAYWARD A. HARVEY, of Orange, New Jersey, have inventeda cert-ain Method of Manufacturing Gimlet-Pointed Rolled Wood-Screws, is a specification.

In the ordinary method of rolling the threads upon screwblanks the action of the dies tends to elongate the body of the blank. In rolling gimlet-pointed screws this is objectionable, because it crowds the metal upon the part of the die which forms the gimlet-point;-and it is further objectionable because the attenuation of the body in a longitudinal direction diminishes to some extent the quantity of metal available for forming a thread projecing laterally outward from the body. By the method which I pursue I produce a screw having its thread formed of two parallel ridges of metal extending outwardly from and spirally around the body and point of the screw and folded together. In the production of this screw the blank, which has first been conically pointed, is introduced between the convex face of a rotating die and the concave face of a stationary die or back-rest. The dies have formed upon their faces series of parallel ribs relatively inclined in opposite directions. The space between the rotating die and the stationary die is so graduated relativelyto the diameter of the blank that the first effect of the dies is to produce a comparatively shallow groove around the body and point of the blank, and to throw up two parallel ridges of metal along the opposite sides, respectively, of such spiral groove. The further action of the dies is to deepen the spiral groove upon the body of the blank, and to increase the height of the parallel ridges and to ultimately fold them together, their apices, at their point ofjunction, forming the apex of the finished thread. In this operation the metal of the blank is gathered together in the spaces between the adjoining ribs of the die, and is therein subjected to transverse compression, the resultant effect of which is to cause the metal to flow laterally outward from the body of the blank, and to thus produce a thread the diameter of which considerably exceeds the diameter of the unthreaded part of the body. The thread upon the conical point of the blank is formed concurrently with the formation of of which the following thethread on the body thereof, and by a similar mode of operation. Owing to the hold which the rotating die maintains upon the metal composing the body of the blank, and the direction in which that metal is displaced in forming the thread, there is no such elongation of the body as causes any difficulty in symmetrically forming the gimlet-thread upon the point.

The accompanying drawings are elevations, respectively representing the screw at five different stages of its manufacture, and are intended to illustrate the character of the progressive action of the dies in rolling the thread upon the body and point by my improved method.

Figure 1 represents the effect produced upon the blank by the dies soon after the commencement of the rolling operation. Figs. 2, 3, and 4 illustrate the character of the progressive modifications in the form of the blank, which finally result in the production of the finished screw, which is shown in elevation in Fig. 5.

On reference to Fig. 1 it will be seen that there is impressed upon the blank A a shallow groove, a, extending spirally around the lower part, B, of the body and around the conical point C, and that the metal displaced in forming the groove a has flowed radially outward and produced along the opposite edges of the groove a the parallel ridges b and 0, respectively.

Fig. 2 illustrates the deepening of the spiral groove a, and the heightening of the ridges b and c, and also their approach to each other.

Fig. 3, illustrating the further effect of the dies, shows the spiral groove (6 to be still deeper, and the ridges b and c thrown still farther out from the body of the blank, and brought together at their bases, the spiral groove a still retaining its V shape in crosssection.

Fig. 4 illustrates the effect produced by the dies in changing the form of thespiral groove a which, it will be seen, is now fiatbottomed, and it will be observed that the ridges Z) and c are folded still closer together and extend still farther outward from the bod of the blank.

Fig. 5 illustrates the final effect resulting from the progressive action of the dies. As

will be seen, the flat-bottomed spiral groove a has been widened to its full width, and the ridges b and 0 have been so compressed together that their apices are united and form the sharp-edged finished thread represented in the drawings.

The effects illustrated in Figs. 1, 2, and 3 may be produced by the'use of a rolling die provided with parallel ribs which are V shaped in cross-section, by gradually increasing the pressure of such die upon the blank from the commencement of the rolling operation to the stage represented in Fig. 3.

The effect illustrated in Fig. 4 can be produced upon a blank brought into the shape illustrated in Fig. 3 by means of a rotating die provided with parallel inclined ribs,

which, instead of being \l' -shaped in crosssection, are truncated, having narrow faces, and conforming in reverse to the shap'e'in cross -section of the groove .a (Shown in" Fig. 4.)

Having been b'roug-ht'into" the condition illustrated in Fig. 4, the screw can be finished the die which first acts upon the blank, and which, by the gradual widening of their apioes, are transformed into the shape of I truncated threads.

I claim as my invention- The herein-described method of forming the threads upon the body and point of gimletpointed screws by means of a die or dies provided with parallel inclined ribs acting to form the convolutions of the thread upon the point and body simultaneously, to wit, first impressing a shallow V-shaped spiral groove upon the body and conical point of the blank, and thereby throwing out from the blank two parallel ridges of metal extending spirally around the body and point between the convolutions of 1 the spiral groove, and then by blank, deepening the spiral groove and enlarging the diameter of the parallel ridges-and folding them together'by transverse compression, then by subjecting the blank to the action of a rolling die, the inclined parallel ribs of which are truncated, transforming the V- s'h'aped spiral groove into a fiat-bottomed spiral groove, displacing the metal from the bases :of the convolutions'of the thread and causing increasing the pressure of the die' upon the 

